Comments on: The Landscape in Scientific American

By: Not Even Wrong » Blog Archive » Does Time Run Backward in Other Universes?

Thu, 22 May 2008 15:44:02 +0000

[...] with major articles promoting the multiverse here, here and here (commentary on this blog here and here). Their latest issue continues in this vein with an article by Sean Carroll entitled Does [...]

By: Not Even Wrong » Blog Archive » The Great Cosmic Roller-Coaster Ride

Not Even Wrong » Blog Archive » The Great Cosmic Roller-Coaster Ride — Mon, 15 Oct 2007 21:48:53 +0000

[...] Scientific American ran a feature article by Bousso and Polchinski promoting the then new idea of The String Theory Landscape. Now that this pseudo-science has become well-entrenched in the physics community, this [...]

By: Not Even Wrong » Blog Archive » Steinhardt on the String Theory Crash

Not Even Wrong » Blog Archive » Steinhardt on the String Theory Crash — Wed, 19 Sep 2007 04:05:25 +0000

[...] Three years ago I expressed the opinion that the promotion of the anthropic landscape would make Einstein gag, which so upset Joe Polchinski that he used this to argue that trackbacks to my blog should not be allowed on the arXiv (even though this was not about an arXiv paper, but a Scientific American article). At one point I regretted having used that expression, feeling it was somewhat over the top and inappropriate. In retrospect, seeing what has happened over the past three years, I’ve changed my mind. The kind of thing that would make Einstein gag has moved from popular science articles to regular appearance in the lectures and scientific articles of leading figures in particle physics. This would probably not just make him gag, but send him into a serious fit of depression. [...]

By: D R Lunsford

D R Lunsford — Wed, 31 Dec 1969 19:00:00 +0000

Not at all. It’s precisely the opposite IMO – they’ve been so poisoned by Bourbakian formalism that they’ve lost their esthetic judgment and are willing to “settle for less”.

My own “feeling” about this is – why should we expect our little efforts to somehow be vastly different from past efforts? That is, whatever works will almost certainly fit nicely into the existing pattern of development, going right back to Air Earth Fire and Water.

To be more precise – a good theory needs a unique context. Every theory to date has provided its own unique context. This even goes for phenomenological theories that work (e.g. BCS – Cooper pairs – WGS – Higgs mechanism etc.)

The thing that gives GR a unique context is background independence.

By: Chris Oakley

Chris Oakley — Wed, 31 Dec 1969 19:00:00 +0000

Well, OK, but then what is it that you are looking for? Interesting mathematics or physics? It seems that fundamental physics has reached its present impasse exactly because people have been – to use Newton’s image – too busy picking up and examining pretty mathematical seashells rather than trying to build a fully consistent understanding of the physical world.

By: D R Lunsford

D R Lunsford — Wed, 31 Dec 1969 19:00:00 +0000

I would not consider it to be gravity, period. There is already a formulation like this for classical GR, which also is not gravity.

Change of space element as in the Pluecker line geoemtry – say, building spacetime and matter from twistors anf getting some sort of quantification from that – might barely make it under the wire.

-drl

By: Chris Oakley

Chris Oakley — Wed, 31 Dec 1969 19:00:00 +0000

If someone came up with a QG model where gravity was just another field on a Minkowski background, which was such that the classical limit gave one Newtonian gravity with light bending, etc. would people just dismiss it as too boring? I ask this question seriously. The main approaches to QG at the moment (Loops and Strings – NB: in alphabetical rather than slice-of-science-budget order) were inspired by, rather than derived from known physics, and in neither case has it been demonstrated that GR emerges as a classical limit. And with regard to Danny’s requirement of background independence, given that SR is one of best verified theories yet, is this requirement not more to do with a feeling of mathematical “rightness” rather than any physics?

By: D R Lunsford

D R Lunsford — Wed, 31 Dec 1969 19:00:00 +0000

In short – anything that claims to extend or sharpen GR will certainly be background-free – that is the unique context that GR introduces. (Every real theory introduces a new physical context.)

-drl

By: JC

JC — Wed, 31 Dec 1969 19:00:00 +0000

Danny,

What would be the dire consequences of a quantum gravity NOT being background free?

I never quite understood the arguments in favor of background independence in quantum gravity. On the surface they so far seem like hand waving arguments, which extrapolate classical general relativity notions and impose them by “decree” in the quantum regime.

By: D R Lunsford

D R Lunsford — Wed, 31 Dec 1969 19:00:00 +0000

The essential thing about gravity, quantum or not, is background-freeness. Clearly you’re never going anywhere without that as the central idea. That’s what makes GR what it is. All this obessive “quantum gravity” kvetsching is just misguided. That will probably take care of itself in it the long run, and probably fix field theory as a side effect. The absolutely key thing is background-free field theory.